Diaphragm Carburetors

[Egebo]

Hi forum.
Im looking for a new carburetor for my old Yamaha FS1 (Good Classic)

I want somthing in the range 18-19mm.
Would prefer 19mm

But the Fs1 original carburetor positioning in the block dosent provide enough space for almost any other type of carburetors.
So i was thinking about getting hold of some kinda diaphragm carburetor, as they are very small.

Should be fairly easy to do.
Just make a new manifold and a vacuum connection to the crankcase.

Would that work?
And are there any 19mm versions?

 

[Browni]

Hi forum.
Im looking for a new carburetor for my old Yamaha FS1 (Good Classic)

I want somthing in the range 18-19mm.
Would prefer 19mm

But the Fs1 original carburetor positioning in the block dosent provide enough space for almost any other type of carburetors.
So i was thinking about getting hold of some kinda diaphragm carburetor, as they are very small.

Should be fairly easy to do.
Just make a new manifold and a vacuum connection to the crankcase.

Would that work?
And are there any 19mm versions?

It can be work! Try to search for the Tillotson carburettors. There are even small sizes too and a lot of them has an independent idle sytem (adjustable idle).

 

[melf #50]

2 times?

is it a Rotating or a membrane inlet?

the manifold should not be a problem , there are Mikuni 16mm that fit espacialy for FS1 , any larger and you will have to adjust the manifold or make one yourself , that is both very simple..

maybe a 18/19/20mm with a loose floater chamber could be somthing , these are very small and not so rare.

 

[Browni]

2 times?

is it a Rotating or a membrane inlet?

the manifold should not be a problem , there are Mikuni 16mm that fit espacialy for FS1 , any larger and you will have to adjust the manifold or make one yourself , that is both very simple..

maybe a 18/19/20mm with a loose floater chamber could be somthing , these are very small and not so rare.

Sorry for the double post. I've already deleted!

 

[Egebo]

2 times?

is it a Rotating or a membrane inlet?

the manifold should not be a problem , there are Mikuni 16mm that fit espacialy for FS1 , any larger and you will have to adjust the manifold or make one yourself , that is both very simple..

maybe a 18/19/20mm with a loose floater chamber could be somthing , these are very small and not so rare.

It is a membrane inlet.
Right now im driving with 16mm manifold, but if i find a 19mm carb ill make a new one.

I was only worried about if the FS1 engine develop an acceptable amount of vacuum for sutch a carburetor.

18-19 mm is fine. 20mm would push the effeiency to high.
I want it to peak at ~ 8750 rpm
At leat that what my homemade expansion chamber is calculated to
Time will show.


Could you give an example of an 19mm with loose floater chamber?

 

[Egebo]

It can be work! Try to search for the Tillotson carburettors. There are even small sizes too and a lot of them has an independent idle sytem (adjustable idle).

Ill try to find a machine witch uses a 19mm tillotson.
Then maby i can get the local "husquana" shop to get one for me.

 

[Cruz_e_Silva]

Try old 70cc petrol woodsaws...New ones only come with 14-16mm tillotsons.
Look in the local shop scrapyard for them. You should find at least 18mm ones from those big engines.